JP3530107B2 - Data recording medium - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data recording medium including a plurality of planar optical waveguide type recording layers having a periodic light scattering factor.

[0002]

2. Description of the Related Art In recent years, there has been a rapid increase in demand for large-capacity memories that are compact and easy to carry, including mobile computing. As one of the methods for realizing a large-capacity memory at low cost, a planar optical waveguide type multiple optical memory is proposed in which data is embedded (recorded) in a planar optical waveguide as a periodic light scattering factor and the optical waveguides are stacked. (See, for example, Japanese Patent Laid-Open No. 11-345419).

FIG. 1 shows an example of a conventional data recording medium of this type together with information reproduction. In the data recording medium 1, a plurality of core layers and clad layers are alternately laminated, or a plurality of core layers sandwiched by clad layers are laminated to form a clad layer (holding layer) above and below the core layer (optical waveguide layer). ) Is a multi-layered planar optical waveguide recording layer.

In each recording layer, the data is a repetitive pitch about the wavelength of light propagating through the optical waveguide layer, which is periodically formed in the optical waveguide layer or the retaining layer near the interface between the optical waveguide layer and the retaining layer. Is recorded as a periodic light scattering factor consisting of a large number of irregularly shaped lines with

Data reproduction is performed by the light 3 emitted from the light source 2.
Is coupled to the incident position 4 of the target recording layer, and the image 5 generated by the light propagating through the recording layer being scattered by the periodic light scattering factor is captured by the image sensor 6.

[0006]

As described above, the data recording medium using the flat optical waveguide type recording layer can be increased in capacity and is promising in the future, but it is possible to secure the data recorded in each recording layer. There was a problem that it had to be separated and reproduced.

An object of the present invention is to reliably reproduce the data recorded in each recording layer in a data recording medium comprising a plurality of planar optical waveguide type recording layers having a periodic light scattering factor. To provide a simple data recording medium.

[0008]

[0009]

[0010]

[0011]

[0012]

[Means for Solving the Problems]
Because, in the present invention consists of the optical waveguide layer and the upper and lower holding layer thereof, the data, the periodic light-scattering factors that reproducibly recorded as an image by scattered light generated when the by propagating light in the optical waveguide layer A data recording medium comprising a plurality of planar optical waveguide type recording layers provided, wherein the periodic light scattering factor is caused in the optical waveguide layer or the holding layer near an interface between the optical waveguide layer and the holding layer. In a data recording medium, which is a plurality of uneven lines having a repeating pitch of about the wavelength of light propagating through the optical waveguide layer, which is formed periodically, the unevenness forming a periodic light scattering factor in each recording layer. line shape, input
Position where the position of the incident light source is fixed and the incident light angle is changed
The position from the light source is different at different positions for each recording layer.
Light incident portions formed with different pitch intervals for each recording layer so as to diffract incident light in a direction that coincides with the optical waveguide layer, and the length or phase of the uneven line shape that constitutes the periodic light scattering factor. Alternatively, a data recording area in which data is recorded is provided.

According to the above structure, in the uneven line of the light incident portion of each of the plurality of stacked recording layers, the direction of the incident light diffracted in the direction coinciding with the optical waveguide layer is different for each recording layer. The position of incident light diffracted in the light incident portion of each recording layer in the direction coincident with the optical waveguide layer is different for each recording layer. Therefore, the incident light diffracted in the light incident portion of the desired recording layer in the direction coinciding with the optical waveguide layer is not diffracted in the light incident portion of the other recording layer in the direction coincident with the optical waveguide layer. Only the desired recording layer is propagated to reach the data recording area, so that only the data recorded in the desired recording layer can be reproduced. In order to reproduce the data recorded in another recording layer, the position of the incident light is changed to select the recording layer in which the direction of the incident light diffracted at the light incident portion matches the optical waveguide layer. It is possible.

Further, according to the present invention, the periodic light composed of the optical waveguide layer and the holding layers above and below the recording layer is used to reproducibly record data as an image by scattered light generated when the light is propagated through the optical waveguide layer. A data recording medium comprising a plurality of planar optical waveguide type recording layers having a scattering factor, wherein the periodic light scattering factor is the optical waveguide layer near the interface between the optical waveguide layer and the holding layer or the optical waveguide layer. In a data recording medium, which is a plurality of uneven lines having a repeating pitch of about the wavelength of light propagating through the optical waveguide layer, which is periodically formed in the holding layer, the recording layer is periodically formed at the same position in each recording layer. line irregularities constituting the light scattering factor, the light incident portion propagation direction of the incident light is diffracted in the direction is formed at an angle of array such that each different direction for each recording layer which is coincident with the optical waveguide layer Along with On the extension line of the propagation direction of the incident light by the light incident part of the recording layer, the data recording area in which the data is recorded by the length and / or the phase of the uneven line forming the periodic light scattering factor is provided. Characterize.

According to the above structure, in the uneven line of the light incident portion of each of the plurality of stacked recording layers, the incident light diffracted in the same direction as the optical waveguide layer propagates in different directions for each recording layer. The incident light diffracted in the direction coincident with the optical waveguide layer at the light incident portion of each recording layer is propagated in a different direction for each recording layer. To reach the data recording area provided on the extension line of the propagation direction. Therefore, the data recorded in all recording layers is reproduced, but the propagation direction of the incident light is different for each recording layer and the position of the data recording area is different for each recording layer. It is possible to select a recording layer for taking out the light.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows a first embodiment of the present invention (however,
Not within the scope of the claims. In the figure, 11 is an optical card (data recording medium), 12 is a detector, 13 is incident light used for reproduction, 14 is propagating light propagating through the recording layer L2, 15 is scattered light, and 16 is Is transmitted light, 17 is diffracted light from the recording layer L1, and 18 is diffracted light from the recording layer L3.

The operation of this embodiment will be described below.

The optical card 11 is a large-capacity read-only memory using a multilayer hologram. It is a transfer type or the like that can be mass-produced, and is capable of accumulating a large amount of data in multiple layers. Specifically, as in the conventional example, a plurality of core layers and clad layers are alternately laminated, or By stacking a plurality of core layers sandwiched by clad layers, a planar optical waveguide type recording layer in which upper and lower sides of a core layer (optical waveguide layer) are held by clad layers (holding layers) is multilayered. FIG. 2 shows an example in which the recording layers L1, L2 and L3 are laminated, but it goes without saying that the number of laminated layers may be larger.

In addition, in each recording layer, the uneven lines forming the periodic light scattering factor are diffracted in a direction that coincides with the optical waveguide layer, and the direction of incident light is different for each recording layer. A light incident portion formed with such a pitch interval, and a data recording area in which data is recorded with the length and / or phase of uneven lines forming the periodic light scattering factor are provided. Reproduction is performed by accurately guiding light to the data recording area of each recording layer.

The periodic light scattering factor is the repetitive pitch of about the wavelength of light propagating in the optical waveguide layer, which is periodically formed in the optical waveguide layer or the retaining layer near the interface between the optical waveguide layer and the retaining layer. It is composed of a large number of lines having unevenness.

A method of reproducing data on the card will be described with reference to FIG.

When the incident light 13 is incident on the light incident part of the optical card 11 at an angle θ0, diffracted light is generated in the direction of the angle θ2 = 90 degrees by the uneven line (pattern) recorded on the recording layer L2. The diffracted light propagates as the propagating light 14 in the optical waveguide layer in the recording layer L2. When the propagating light 14 arrives at the data recording area where data is recorded in the length and / or phase of the pattern, the light is scattered by this pattern and scattered light 15 is generated. This scattered light 15 is detected by the detector 12
The data can be reproduced by detecting with. The detector 12 is preferably a two-dimensional sensor array such as a CCD or CMOS sensor.

FIG. 2B shows how diffracted light is generated by the light incident portion of each recording layer with respect to the incident light 13.

When the incident light 13 is incident at an angle θ0, the angle θ1 of the diffracted light 17 from the light incident portion of the recording layer L1 of the optical card 11 is as follows.

In the pattern recorded on the light incident portion of the recording layer L1 of the optical card 11, assuming that the pitch interval (fundamental period) of the pattern is d1, sin (θ1) −sin (θ0) = a · λ / d1 Required by. Here, λ is the wavelength of light in the optical card, and is a value obtained by dividing the wavelength in air by the refractive index n of the optical card. Since n is around 1.5, the wavelength in the optical card is about 0.67 times that in air. In addition, a represents the order of the diffracted light to be used, and here, the + 1st order diffracted light, that is, a
= + 1.

Similarly, when the incident light 13 is incident at an angle θ0, the diffracted light from the light incident portion of the recording layer L2 of the optical card 11 propagates as propagating light 14 in the optical waveguide layer in the recording layer L2. The angle θ2 is set to 90 degrees and has the following relationship.

In the pattern recorded on the light incident part of the recording layer L2 of the optical card 11, the basic period of the pattern is d2.
Then, sin (θ2) −sin (θ0) = a · λ / d2.

Similarly, when the incident light 13 is incident at the angle θ0, the angle θ3 of the diffracted light 18 from the light incident portion of the recording layer L3 of the optical card 11 is as follows.

In the pattern recorded on the light incident portion of the recording layer L3 of the optical card 11, the basic period of the pattern is d3.
Then, sin (θ3) −sin (θ0) = a · λ / d3.

Thus, the direction of the diffracted light can be changed by changing the basic period of the pattern recorded on the light incident portion of each recording layer. Here, an example in which the + 1st-order diffracted light is used is shown, but the −1st-order diffracted light (a = −1) may be used, and higher-order diffracted light (a = + 2, + 3,
.., or a = -2, -3, ...) can also be used.

FIG. 3 shows an example of the data recording area of each recording layer together with the detection of scattered light (reproduction data). FIG. 3A shows the data reproduction from the recording layer L2. (B) shows a plan view.

When the propagating light 14 propagates in the recording layer L2 from the light incident portion and reaches the data recording area, scattered light 15 is generated by the pattern recorded in the data recording area of the recording layer L2 of the optical card 11. Data can be reproduced by taking in the scattered light 15 by the detector 12. In order to read the pattern recorded in the data recording area of the recording layer L1, the incident angle of the light incident on the light incident portion is changed so that the diffracted light propagates through the optical waveguide layer in the recording layer L1. Similarly, in order to read the pattern recorded in the data recording area of the recording layer L3, the incident angle of the light incident on the light incident portion is changed so that the diffracted light propagates through the optical waveguide layer in the recording layer L3. To In this way, by adjusting the angle of incident light, it is possible to control the propagation of light and detect the data recorded in each layer separately.

FIG. 4 shows a specific example of the pattern of the light incident portion of each recording layer, here an example formed by changing the basic period of the above-mentioned pattern. 111 is the pattern of the recording layer L1 and 112 is the recording layer. L2 pattern, 113 is recording layer L
3 pattern. The pattern formed on the light incident part is
It is a good example to form the optical waveguide layer (core layer) by lowering the refractive index of the protective layer (cladding layer) surrounding it and making the interface between the core layer and the cladding layer uneven. Thus, by changing the basic period, the recording layer through which the light propagates changes depending on the angle of the incident light, and the data in each layer can be separated and reproduced.

FIG. 5 shows another example of the pattern of the data recording area of each recording layer as well as the data reproduction. FIG. 5A shows the data reproduction from the recording layer L2, and FIG. A state of data reproduction from the recording layer L3 is shown.

Regarding the pattern of the data recording area, the refractive index of the protective layer (cladding layer) that surrounds the optical waveguide layer (core layer) is set to be low, and the interface between the core layer and the cladding layer is made uneven. This is a good example. In FIG. 3, the basic period of the pattern of the data recording area of each layer is the same, but in FIG. 5, the basic period of the pattern of the data recording area of each layer is the same as the basic period of the pattern of the light incident portion of each layer. There is. This way,
The basic period of the pattern formed on each recording layer can be unified, and the manufacturing becomes easy.

However, scattered light from the data recording area (1
Since the direction (5, 19) changes depending on the basic cycle of the pattern, it is a good example to change the recording position of the data recording area according to the basic cycle of the pattern. Further, the position of the detector 12 may be changed for each recording layer, that is, for each basic period of the pattern.

FIG. 6 shows the second embodiment of the present invention, in which the light incident portion of each recording layer of the optical card is shown. In the first embodiment, an example in which the basic period of the pattern of the light incident portion recorded in each layer is changed is shown. In this embodiment, an example in which the position of the pattern of the light incident portion recorded in each layer is changed is shown. Show.

FIG. 6A shows a pattern 21 of the first layer formed in the center of the light incident portion, and FIG. 6B shows a pattern 22 of the second layer formed on the left side of the light incident portion. 6 (c) shows the pattern 23 of the third layer formed on the right side of the light incident portion.

As described above, when the position of the light incident part changes, the angle of the incident light changes (however, it is assumed that the position of the light source of the incident light is constant), whereby the recording layer for propagating the light can be selected. Here, an example is shown in which the light incident part is shaken to the left and right, but it is also a good example to shake it vertically with respect to the paper surface. Further, although the example in which the basic period of the pattern is the same is shown, it is also a good example to form the light incident part by changing both the position and the basic period of the pattern. By combining both, more layers can be selected.

FIG. 7 shows a third embodiment of the present invention, in which each recording layer of an optical card is shown. In the first and second embodiments, the recording layer that propagates light is selected, but in this embodiment, the direction in which light is propagated is selected to select each recording layer. Indicates.

FIG. 7A shows the first layer pattern 31 consisting of the light incident portion pattern 31a and the data recording area pattern 31b, and FIG. 7B shows the light incident portion pattern 32a.
And the pattern 32b of the data recording area, the second layer pattern 32 is shown in FIG.
The pattern 33 of the third layer, which is composed of a and the pattern 33b of the data recording area, is shown.

The pattern 32a of the light incident portion of the second layer is formed so that the light propagates horizontally with respect to the paper surface. The light incident on the pattern 32a propagates horizontally with respect to the paper surface, and the pattern of the data recording area. Light is scattered by 32b and emerges. The light is detected by a detector (not shown) arranged on the front side or the back side of the paper to reproduce the data.

The pattern 31a of the light incident portion of the first layer is formed in the lower right direction with respect to the paper surface, and the incident light propagates in the lower right direction of the paper surface. Therefore, the position of the light incident part is
Even in the same layer, the data of the pattern 31b in the data recording area of the first layer can be detected by changing the position of the detector downward. Similarly, the pattern 33a of the light incident portion of the third layer is formed so as to rise to the right with respect to the paper surface, and the incident light propagates in the upper right direction on the paper surface. Therefore, even if the position of the light incident portion is the same as that of the first layer and the second layer, the data of the pattern 33b of the data recording area of the third layer can be detected by changing the position of the detector upward.

In this way, by changing the pattern inclination (array angle) for each layer, the position of the data recording area can be changed even if the position of the light incident portion is the same. The formed data can be selectively reproduced.

Further, by using the above-described embodiments in combination, a higher density card recording can be realized.

As for the irregular-shaped line which constitutes the periodic light scattering factor, the refractive index of the holding layer (cladding layer) surrounding the optical waveguide layer (core layer) is set to be low, and the core layer and the cladding layer are Although it has been shown that the interface is formed by providing unevenness on the interface, other ions may be implanted into the core, or an optical uneven shape may be formed by applying strain.

[0048]

[0049]

[0050]

As described above , according to the present invention,
The uneven line of the light-incident part of each of the recording layers stacked is
Since the direction of the incident light diffracted in the direction coincident with the optical waveguide layer is formed in a position different in each recording layer, the direction in which the light incident part of each recording layer coincides with the optical waveguide layer. The position of the incident light diffracted into is different for each recording layer.
Therefore, the incident light diffracted in the light incident portion of the desired recording layer in the direction coinciding with the optical waveguide layer is not diffracted in the light incident portion of the other recording layer in the direction coincident with the optical waveguide layer. Only the desired recording layer is propagated to reach the data recording area, so that only the data recorded in the desired recording layer can be reproduced. Therefore, data can be recorded with high density and the recorded information can be separately reproduced only by changing the position of the incident light.

Further, according to the present invention, in the uneven line of the light incident portion of each of the recording layers stacked, incident light diffracted in a direction coinciding with the optical waveguide layer is different in each recording layer. The incident light diffracted in the light incident portion of each recording layer in a direction coinciding with the optical waveguide layer is propagated in a different direction for each recording layer. It reaches a data recording area provided on an extension of the propagation direction of incident light. Therefore, the data recorded in all recording layers is reproduced, but the propagation direction of the incident light is different for each recording layer and the position of the data recording area is different for each recording layer. It is possible to select a recording layer for taking out the light. Therefore, the data can be recorded at a high density and the recorded information can be separately reproduced only by changing the position of the detector.

According to these inventions, the light incident portion and the data recording area can be formed in the same process, and the light incident position on the data can be accurately formed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of a conventional data recording medium.

FIG. 2 is a configuration diagram showing a first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing an example of a data recording area according to the first embodiment.

FIG. 4 is a configuration diagram showing a specific example of a pattern of a light incident portion according to the first embodiment.

FIG. 5 is a configuration diagram showing another example of a data recording area in the first embodiment.

FIG. 6 is a configuration diagram showing a second embodiment of the present invention.

FIG. 7 is a configuration diagram showing a third embodiment of the present invention.

[Explanation of symbols]

11: optical card, 12: detector, 13: incident light, 14:
Propagated light, 15, 19: scattered light from the recording layers L2, L3,
16: transmitted light, 17, 18: diffracted light from the recording layers L1, L3, 21, 22, 23: patterns of light incident portions of the first, second, and third layers, 31, 32, 33: first, first Second, third layer patterns, 111, 112, 113: recording layers L1, L
Patterns of light incident portions of L2 and L3.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI G06K 19/00 D (72) Inventor Masahiro Ueno 2-3-1, Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72 ) Inventor Manabu Yamamoto 2-3-1, Otemachi, Chiyoda-ku, Tokyo Within Nippon Telegraph and Telephone Corporation (56) References JP-A-9-101735 (JP, A) JP-A-10-83135 (JP, A) JP 11-337756 (JP, A) JP 11-345419 (JP, A) JP 2000-19938 (JP, A) JP 2000-19939 (JP, A) International Publication 01/057602 (WO, A1) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B ⁷ /00-7/135 G03H 1/00-5/00 G06K 7/00-7/14 G06K 19/00-19/08 G11C 13/00-13/08

Claims (2)

(57) [Claims] 1. A periodic light scattering factor, which comprises an optical waveguide layer and holding layers above and below the optical waveguide layer, for reproducibly recording data as an image of scattered light generated when light is propagated through the optical waveguide layer. In the data recording medium comprising a plurality of planar optical waveguide type recording layers, the periodic light scattering factor is periodic in the optical waveguide layer near the interface between the optical waveguide layer and the holding layer or in the holding layer. In a data recording medium, which is a plurality of uneven lines having a repeating pitch approximately equal to the wavelength of light propagating through the optical waveguide layer, a concave and convex shape forming a periodic light scattering factor in each recording layer. Line of incident light
At a position where the position of the light source is fixed and the angle of incident light is changed
Incident from the light source at different positions for each recording layer.
The light incident portions formed with different pitch intervals for each recording layer so as to diffract the light in the direction that coincides with the optical waveguide layer, and the length or phase of the uneven lines forming the periodic light scattering factor or A data recording medium having a data recording area for recording data on both sides. 2. A periodic light scattering factor, which comprises an optical waveguide layer and holding layers above and below the recording layer, for reproducibly recording data as an image of scattered light generated when light is propagated to the optical waveguide layer. In the data recording medium comprising a plurality of planar optical waveguide type recording layers, the periodic light scattering factor is periodic in the optical waveguide layer near the interface between the optical waveguide layer and the holding layer or in the holding layer. In the data recording medium, which is a plurality of uneven lines having a repeating pitch of about the wavelength of the light propagating through the optical waveguide layer, a periodic light scattering factor is applied to the same position of each recording layer. line irregularities constituting the light entrance portion propagation direction of the incident light is diffracted in the direction is formed at an angle of each become different directions by <br/> intends Do arrangement for each recording layer which is coincident with the optical waveguide layer And the light of each recording layer Data characterized by providing a data recording area in which data is recorded with the length and / or phase of the uneven line shape that constitutes the periodic light scattering factor on the extension line of the incident light propagation direction by the projecting section. recoding media.